Park Tool Chain Checker CC-4.2The Park Tool CC 4. 2 Chain Checker measures bicycle chain wear. The laser cut CC 4. 2 accurately measures a long section of chain and strategically comes in contact with the chain in three places, quickly and easily taking the guesswork out of determining when chain replacement is necessary. The tool works on any 5 to 13 speed derailleur chain (including SRAM T Type, SRAM Flattop, Shimano XTR 12 speed, and Campagnolo Ekar 13 speed chains) or single